E-cadherin expression in human breast cancer cells suppresses the development of osteolytic bone metastases in an experimental metastasis model.

The molecular mechanisms by which human cancer cells spread to bone are largely unexplored. The process likely involves cell adhesion molecules (CAMs) that are responsible for homophilic and heterophilic cell-cell interactions. One relevant CAM may be the calcium-dependent transmembrane glycoprotein E-cadherin. To investigate the involvement of E-cadherin in breast cancer metastasis to bone, we used an in vivo model in which osteolytic bone metastases preferentially occur after injections of cancer cells directly into the arterial circulation through the left ventricle of the hearts of nude mice. We have found that E-cadherin-negative human breast cancer cells MDA-MB-231 (MDA-231) develop radiographically detectable multiple osteolytic bone metastases and cachexia in this model. However, MDA-231 breast cancer cells that were transfected with E-cadherin cDNA showed a dramatically impaired capacity to form osteolytic metastases and induce cachexia. Histological and histomorphometrical analyses of bones of mice bearing mock-transfected MDA-231 revealed aggressive metastatic tumor, whereas metastatic tumor burden was significantly decreased in the bones of mice bearing E-cadherin-expressing MDA-231. Nude mice bearing E-cadherin-transfected MDA-231 breast cancer cells survived longer than mice bearing mock-transfected MDA-231 breast cancer cells. Anchorage-dependent and -independent growth in culture and tumor enlargement in the mammary fat pad of nude mice were unchanged between mock-transfected and E-cadherin-expressing MDA-231, suggesting that these differences in metastatic behavior are not due to an impairment of cell growth and tumor-igenicity. Our results show the suppressive effects of E-cadherin expression on bone metastasis by circulating breast cancer cells and suggest that the modulation of expression of this CAM may reduce the destructive effects of breast cancer cells on bone.